Author Topic: Screwcutting drop in dial  (Read 6154 times)

bogstandard

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Screwcutting drop in dial
« on: March 10, 2009, 02:49:03 PM »
Another backlog project bites the dust.

No production pictures this time, just machined parts to do the job.

Just a little history to tell you why I did this mod.
On larger metric machines, as you go from one range of pitch threads to another, you have to remove the drop in dial and replace the gear on the end of the spindle, to allow the gear system to stay synchronised with the large leadscrew.

My machine uses three gears, just like the ones below, with 14, 15 and 16 teeth. It would be a real PITA to keep changing these gears, so I modified my block to like others I had seen, which had a ganged gear set




The first job was to get rid of the loose bolt that went thru the block, had a spacer fitted and then screwed into the side of the saddle. I made a standout with a built in spacer.
If you notice, the leadscrew guard has been removed, that was because it cramped my overall saddle travel a little, and I don't know if this mod would still work with the guard in place.




The main part of the job was to skim the two larger gears to half their width. This was to allow the gears to be fitted together, but still allow one gear to mesh with the leadscrew without it fouling the other gears.




The next job was to make two more holes in the main block at 12.5mm pitch between centres.




A spin handle was made up to match the rest of the handles on the machine, straight sides dropping down to a taper.




This is shown set up for the 15 tooth gear. Notice how the 16 tooth now clears the leadscrew.




This one shows the 16 tooth in synch with the leadscrew. It takes only seconds to switch from one size to another, plus I won't have to go searching around to find where I had put the spare gears.




Next one to get out of the way, make 3 flywheels from plate material.


Bogs

Offline Twinsquirrel

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Re: Screwcutting drop in dial
« Reply #1 on: March 10, 2009, 02:57:06 PM »
What a great idea :smart:, my mini lathe uses a similar system of gears.....another project or the list!!! :scratch:
So many ideas, so little skill

bogstandard

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Re: Screwcutting drop in dial
« Reply #2 on: March 10, 2009, 03:07:44 PM »
There is in fact another part to be made for this mod.

The fixed scale on top of the block needs to be made adjustable, so the pointer can be moved the the exact position for drop in. I will do that next time I have the RT on the mill.

The only other way would be to fit a very strong spring between the block and the standout spacer, and by screwing the block in and out, the same effect would be achieved.

Watch this space.

Bogs.

Offline sbwhart

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Re: Screwcutting drop in dial
« Reply #3 on: March 10, 2009, 05:07:00 PM »
Nice Job John  :thumbup:

I didn't really appreciate what you were doing when I saw it on Saturday great idea  :clap:

Stew
A little bit of clearance never got in the road
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Location:- Crewe Cheshire

Offline John Hill

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Re: Screwcutting drop in dial
« Reply #4 on: March 10, 2009, 05:27:21 PM »
Nice work Mr Standard, an elegant solution to the clumsy "little-pinion-dropping-in-the-swarf-bucket" problem too.

I must confess though my machine is apparently a close kin of yours I dont think I will be doing this, so far I take the easy way out and just motor back to the starting point.  Obviously there are some (quite a few no doubt) aspects of this pastime still to be learned in the Bodger's Lair.
From the den of The Artful Bodger